This invention relates generally to an apparatus used for the zigzag folding of a web, and more particularly to such an apparatus having at least one channel guide for the folding operation which is engageable with the apparatus at a selected and changeable pivot point for adjusting the oscillation amplitude thereof.
A typical folding apparatus for the zigzag folding of webs of paper or other materials is operatively connected to a printer so that the forms printed from webs of indeterminate length may be conveniently fan-folded or zigzag folded along lines of weakening disposed transversely to the direction of feed of the web through the printer. The spacing of these lines of perforations corresponds to the particular size of the series-connected sheets or formats of the web to be printed. The folding apparatus must therefore be adjusted to accommodate differently sized series-connected sheets from one folding operation to the next.
U.S. Pat. No. 3,889,940, commonly owned herewith, represents an improvement over German Pat. No. 1,070,010, dated May 12, 1960, also commonly owned herewith. In this U.S. Pat., a web guide or channel is provided through which the web to be folded passes, and the guide is connected at opposite ends with the oscillation means. This oscillation may be positively adjusted to accommodate varying form sizes so as to assure that the web is folded along its transverse lines of weakening during each folding operation. However, in both the aforementioned U.S. and German patents, the channel guides are mounted for movement on the machine about stationary pivots, and the cam members to which the channel guides are connected are adjustable toward and away from the channel guides so as to adjust the amplitude of the reciprocating channel guides. In U.S. Pat. No. 3,889,940, the entire disclosure of which is specifically incorporated herein by reference, pivot pins 10 and 11 for the connected channel guides are fixedly secured to the machine frame and the respective pins at opposite sides of the guide are co-axial so that the channel guide is pivoted about these pins.
However, with the currently available high speed printers, the web channel guide must be oscillated at high frequencies in accordance with web velocity, and the oscillation frequencies are even further increased to accommodate the folding of small-sized sheets as when the transverse lines of weakening are spaced closely together. Therefore, at high running printer speeds, especially during the folding of series-connected sheets having small spaced transverse lines of weakening, the oscillation forces to which the channel guides are subjected are intensified to such an extent as to affect the smooth folding operation of the machine. The presently available zigzag folding apparatuses are limited in their capacity for oscillating at certain high frequencies required for a particular folding operation.